All thanks to @polyg, I got to go and see my first ever rehearsed reading last Friday. It was for a play called The Lost Mariner by Nick Payne as part of Royal Court's rough cuts season in the Jerwood Upstairs.
As I discovered, a rehearsed reading is a run through, with real actors, scripts in hand, of a work in progress. It was 40-minutes long and absolutely terrific. Only the presence of the scripts and page turning made it feel any different to a fully formed production.
The play was about a man, Jimmy, who believes it is still 1995 and has short term memory loss. While he can't remember things like being asked to hold a carrot moments earlier only to be surprised to find it in his hand, he also doesn't recognise his 15-years-older son and wife.
His family do everything they can to try and trigger some sort of memory and struggle to cope with this unintentionally cruel form of rejection.
It was both funny and moving and I left wanting more. I'm curious to see how it evolves into a fuller play and I'll certainly be keeping an eye for it in the future.
* I've subsequently discovered from @sjc_home4tea that the Caryl Churchill readings I went to at the Royal Court in 2008 are technically rehearsed readings. So this counts as my first rehearsed reading of a play in progress.